The following is a list of commonly used LINUX/UNIX commands which may be of value during your Telnet sessions. Remember that LINUX/UNIX is case sensitive. Options or flags which can be used with a command are placed in [ ]. The [ ] are not part of the command and should not be included in the command that you type.

login username

allows you to login for a Telnet session

passwd

changes your password

logout

logs you out of a Telnet session

cd

change directory; cd .. moves you backwards to the next higher subdirectory level; cd / moves you to the highest directory level

chmod permissions filenames

changes the permissions for a file; permissions should include a letter
designating who gets permissions (u for the user, g for the group, o for others, or a for all) followed by a + or – (to give or take away the permission) followed by the kind of permission (r for read access, w for write access, xfor execute if the file is a program or script); the complete command that you type should look like:chmod g-w filename

chown user:group filenames

changes ownership of a file

clear

clears the screen

cp oldfiles newfiles

copies a file; this leaves the old file intact and makes a new copy with a new filename

date

tells you the current date and time

df

displays how much space on the disks (harddrive partitions) is free

du [-a] [-s] directories

tells you how much disk space your files occupy; the -a option displays the space used by each file, not just each directory; the -s option displays the total space used for each directory but not subdirectory

finger username@servername

provides information concerning a user; finger without the username@servername will provide information concerning who is using the server at that time

help

provides online help; several topics have been included in the help system available on the servers

ls [-l] [-a] [-p] [-r] [-t] [-x]

lists the files in a directory; -l displays detailed informtion about each file and directory, including persmissions, owners, size and time/date when the file was last modified; -a option displays all the files and subdirectories including hidden files (with names that begin with a dot); -p displays a slash at the end of each directory name to distinguish them from filenames; -r displays files in reverse order; -t displays files in order of modification time; -x displays the filenames in columns across the screen.

lynx servername or URL

Lynx is a text-based, non-graphical web browser for use in Telnet session

man [-k keywords] topic

displays the reference manual page about a LINUX command; the –k keywords option allows you to see all man pages that contain that keyword; topic is the command or topic which you want information about

mesg [n|y]

lets you control whether other people can use the talk command to interrupt you with on-screen messaging; mesg n will block the interruptions; mesg y will allow interruptions

mkdir new_directory

makes a new subdirectory with the name specified by new_directory

mv [-i] oldname newname

renames a file or moves it from one filename or directory to another; the -i option tells mv to prompt you before it replaces an existing filename

nslookup IP address or server alias

provides conversion of an IP address to an alias of a computer if it is registered in DNS (Domain Name Service) or will provide the IP address for an alias

passwd

changes your password

pine

a program which allows you to read and send mail; information concerning the use of pine can be found elsewhere in the documentation or by reading the online manual pages for pine ( man pine )

ping IP address or server alias

sends a ping packet to another server; this provides information concerning the time it takes for information to make the round trip to the other computer; it will also tell you whether the other server is on-line at that time

ps

displays information about your processes/jobs/programs which are running on the server

rm [-i] [-r] filenames

removes or deletes files; the -i option asks you to confirm that you want to delete each file; the -r option is dangerous because it allow you to delete an entire directory and all of the files it contains

rmdir directory

removes a directory; you can use the -i and -r options which are described in the rm command

tail [-r] [-lines] filename

displays the last few lines of a file; -r displays the lines in reverse order; -lines specifies the number of lines, starting at the end of the file, you want to see

talk username@servername

allows you to talk to another user by typing messages to each other on-screen; to prevent someone from talking to you, see the mesg n
command

touch [-a] [-c] [-m] [date] filenames

changes the date and time for a file without changing the content of the file; -a changes onlyt the date and time the file was last accessed; -c doesn’t create a file if it does not already exist; -m changes only the date and time the file was last modified; date specifies the date and time to give the file in the mmddhhnn format (month, day, hour, minute); touch with a new filename with create a new, empty file.

traceroute IP address or server alias

provides information concerning the route which packets must take to get from your computer (the server in this case) to a remote computer/server; typically used to diagnose possible problems in packet routing